1. Field of the Invention
The present invention relates to a pump apparatus for multiple purposes, which can continuously pump and transfer liquid even containing a large amount of foams, but also can make high-level defoaming function, degassing function, pumped liquid sterilizing function, etc.
2. Description of the Prior Art
It is generally thought difficult to pump and transfer liquid containing a large amount of foams with pumps. Specifically centrifugal pumps have a problem that they do not find it easy to continuously pump and transfer such liquid while removing the foams even in use together with vacuum means for degassing.
The art which has clearly solved this problem is the invention xe2x80x9ca centrifugal pumpxe2x80x9d described in the specification of Japanese Patent Publication No. 3655/1965. (This invention will be hereinafter called xe2x80x9cOriginal Invention 1xe2x80x9d.) In Original Invention 1, a primary pump for pumping liquid is equipped with a sub-pump for drawing a cavity, which has a suction port disposed in communication with a vicinity of the center of the impeller of the primary pump and a discharge port in communication with the suction port of the primary pump, and a degassing path is provided from a vicinity of the center of the impeller of the sub-pump to the vacuum means, whereby a cavity in the vicinity of the center of the impeller of the primary pump is forcedly removed so as to keep the pumped liquid always uninterrupted.
An improvement of Original Invention 1, in which a safety valve which is opened and closed by a negative pressure generated by the vacuum means which is inserted in the degassing path so as to prevent malfunctions of the vacuum means due to intrusion of the pumped liquid during a pause of the pump is the invention xe2x80x9ca self-priming centrifugal pumpxe2x80x9d described in the specification of Japanese Patent Publication No. 3145/1967. (This invention will be hereinafter called xe2x80x9cOriginal Invention 2xe2x80x9d.)
An improvement of Original Invention 2, in which safety means, such as a valve mechanism or others, comprising a delayed operating valve, a quick valve, etc. is inserted in the degassing path, whereby the intrusion of liquid into the vacuum means from the primary pump can be securely prevented throughout all the processes of pump actuation, operation and stop is the invention xe2x80x9ca self-priming centrifugal pumpxe2x80x9d described in the specification of International Publication WO98/04833 (International Application PCT/JP97/00857). (This invention will be hereinafter called xe2x80x9cOriginal Invention 3xe2x80x9d.)
As exemplified in FIG. 12, the pump apparatus according to Original Invention 3 comprises a primary pump 1, a sub-pump 4 and vacuum means 12. A vicinity of the center of the primary pump impeller 2 is in communication with the suction port c of the sub-pump 4. The sub-pump discharge port d is in communication with the primary pump suction port a through a return flow path e. A vicinity of the center of the sub-pump impeller 5 is connected to the vacuum means 12 through a degassing path h. In the degassing path h, a delayed operating valve 13 which is opened at a lag from a time upon injection of a power input of the motor of the pump apparatus and a quick valve 14 which is closed immediately upon turn-off of the power of the motor are serially inserted. In the pump apparatus shown in FIG. 12, wherein the vacuum means 12 is provided by a fluid ring vacuum pump. The delayed operating valve 13 is opened at a delayed time by an internal pressure in the valve drive chamber w gradually increasing as a hydraulic pressure of the operational fluid of the fluid ring vacuum pump is increased.
The pump apparatus shown in FIG. 13 is proposed as one embodiment of original Invention 3. In this pump apparatus, a communication passage from a vicinity of the center of the impeller 2 of the primary pump to the suction port c of the sub-pump is open to a part where a cavity is generated, on the suction side of the primary pump impeller 2, a helical inlet is formed on the suction side of the primary pump impeller 2, and a smaller-bore impeller 23 which is rotated, interlocked with the primary pump is provided, so as to draw the gas in the cavity with a shape as defined by the dot line in FIG. 13 formed on the suction side of the primary pump impeller 2.
The pump apparatus of Original Invention 3 can easily suck liquid containing a large amount of foams, slurries, etc., also can prohibit intrusion of the liquid from the primary pump into the vacuum means throughout all the processes of actuation, operation and stop of the pump, and can be completely automatically operated and is a very practically useful device. However, the pump apparatus still has a problem to be solved. The problem is its gas-liquid separation which can be used in simply pumping liquid but is insufficient in higher-level applications, e.g., higher-level defoaming, degassing for extruding gas dissolved in the pumped liquid, etc.
For advancing the gas-liquid separation, specifically for removing gas dissolved in the pumped liquid, it is known to dispose a resisting object, such as an orifice or others, in the flow path to decompress the pumped liquid, or to raise the temperature of the pumped liquid. However, what is important is how to perfectly trap the gas which has been separated, so that the gas can be perfectly separated from the pumped liquid. For higher defoaming and degassing achievements, the vacuum means must be accordingly efficient, which means the pumped liquid tends to be drawn, with mixed gas, into the vacuum means. Accordingly, the gas-liquid separation must be sufficiently made before the degassing.
In the pump apparatus of original Invention 3, basically a centrifugal force for the gas-liquid separation is generated by rotation of the primary pump impeller 2. However, concurrently therewith, strong vortexes and turbulent flows are produced, and a part of foams cannot be centrifuged for separation and will be entrained on the vortexes and turbulent flows of the pumped liquid and go out to the primary pump discharge port b. Thus the gas-liquid separation is not always sufficient. Even in the pump apparatus shown in FIG. 13, comprising the smaller-bore impeller 23 rotatably interlocked with the primary pump impeller 2, the smaller-bore impeller 23 only plays the role of retaining a cavity unbroken, which is produced by the helical inlet on the suction side of the primary pump impeller 2. Also in the primary pump impeller 2, a part of the foams which has escaped the centrifugation will be entrained on the pumped liquid to be carried to the primary pump discharge port b.
As the generally used conventional art, the cyclone-type gas-liquid separating mechanism comprising the helical inlet is widely used. The mechanism depends on whirling force generated by kinetic energy of the pumped liquid itself and cannot make sufficient gas-liquid separation.
An object of the present invention is to provide a multipurpose pump apparatus of high achievement which can solve by a simple constitution the problem still left unsolved by Original Invention 3, and which incorporates a gas-liquid separation mechanism, etc. stably and without failure operative to make high-level defoaming function and degassing function and further pumped liquid sterilizing function, etc.
To attain the above-described object the pump apparatus according to the present invention comprises a gas-liquid separating apparatus with a gas-liquid separating impeller being inserted in a pumped liquid flow path of a primary pump for liquid pumping; a cavity receiver receiving the tail bottom of a tornado-shaped cavity produced by rotation of the gas-liquid separating impeller to prevent the tornado-shaped cavity from extending; and vacuum means connected to a part in a vicinity of the center of the tornado-shaped cavity through a degassing path.
A pump apparatus according to another invention comprises a gas-liquid separating impeller disposed in a pumped liquid flow path of a primary pump for liquid pumping with a primary pump impeller; a cavity receiver receiving the tail bottom of a tornado-shaped cavity produced by rotation of the gas-liquid separating impeller to prevent the tornado-shaped cavity from extending; and vacuum means connected to a part in a vicinity of the center of the tornado-shaped cavity through a degassing path.
In the present invention, a part in a vicinity of the center of the primary pump impeller may be also connected to the vacuum means through a degassing path;
the primary pump impeller and the gas-liquid separating impeller may be disposed adjacent to each other;
a flow path on the suction side of the gas-liquid separating impeller may be formed in a shape by which a liquid is drawn into a direction of rotation of the gas-liquid separating impeller;
throttle means for decompressing a pumped liquid may be inserted in the flow path on the suction side of the gas-liquid separating impeller;
heating means for the pumped liquid may be inserted in the flow path on the suction side of the gas-liquid separating impeller;
cavitation causing means may be disposed in the pumped liquid flow path;
constituent members of the primary pump may be formed in a configuration which tends to cause cavitation;
the gas-liquid separating impeller may be formed in a configuration which tends to cause the cavitation;
breaking means for breaking foreign objects in the pumped fluid may be further disposed;
protection means which allows gas to pass but prevent liquid from passing may be inserted in the degassing path;
a sub-pump including an impeller may be disposed; the degassing path may be in communication with the suction port of the sub-pump; the discharge port of the sub-pump may be in communication with the suction side of the primary pump through a return path; and a part in a vicinity of the center of the sub-pump impeller may be in communication with the vacuum means;
valve means which is opened at a lag from a time when an operating power of the sub-pump is injected and closes immediately at a time when the driving force of the sub-pump is shut off may be inserted in the degassing path;
the discharge port of the vacuum means may be in communication with the discharge side of the primary pump through a return path;
at least two of the primary pump, the gas-liquid separating impeller, the sub-pump and the vacuum means may be coaxial with one rotary shaft system; and
the gas-liquid separating impeller and the cavity receiver may be disposed in multi-stages.
Because of such constitution, in the pump apparatus according to the present invention, when liquid is pumped by the primary pump, foams in the pumped liquid are forcedly centrifuged by the gas-liquid separating impeller, a tornado-shaped cavity produced near the center of the gas-liquid separating impeller has the tail bottom received by the cavity receiver to be prevented from extending, the gas is drawn by the vacuum means from a part in a vicinity of the center of the cavity through the degassing path, whereby strong defoaming function can be made.
Gas dissolved in the pumped liquid is separated by decompression or others, and the generated foams are forcedly centrifuged by the gas-liquid separating impeller. Thus, strong degassing function is made.
Cavitation is caused in the pumped liquid after degassed, whereby sterilizing function, etc. can be made.
The intrusion of the pumped liquid into the vacuum means is prevented, whereby safe control of the pump apparatus can be perfect, and foreign objects in the pumped liquid can be broken. The pump apparatus can be easily applied to various applications.